Vacuum sense control for phaco pulse shaping

ABSTRACT

A method and apparatus for precisely controlling particle movement relative to a phacoemulsification needle tip is provided. The design monitors actual vacuum present and calculates a pulse shape amplitude waveform proportional to the amount of measured vacuum. An increase in vacuum indicates that the handpiece/needle is becoming occluded by a large particle. The present design determines whether additional power is required to bump or move a large particle away from the needle tip. The present design may employ a control loop that senses and continuously monitors vacuum. The design may dynamically vary the amount of ultrasonic energy delivered to the surgical area in response to the observed actual vacuum, and can actively vary the amount of power delivered to the surgical area based on the size of the particle and the resultant vacuum realized.

This application is a divisional of and claims priority to U.S.application Ser. No. 13/473,959 filed on May 17, 2012, which is acontinuation U.S. application Ser. No. 13/196,559 filed on Aug. 2, 2011,now U.S Pat. No. 8,202,287, that issued on Jun. 19, 2012, which is acontinuation of U.S. application Ser. No. 12/684,657, filed on Jan. 8,2010, now U.S. Pat. No. 7,998,156, that issued on Aug. 16, 2011, whichis a continuation of U.S. application Ser. No. 11/461,741 filed on Aug.1, 2006, now U.S. Pat. No. 7,785,336, that issued on Aug. 31, 2010 eachof which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of surgical tissueremoval, and more specifically to ultrasonic power delivery duringsurgical tissue removal procedures such as phacoemulsification.

2. Description of the Related Art

Phacoemulsification surgery has been successfully employed in thetreatment of certain ocular problems, such as cataracts.Phacoemulsification surgery utilizes a small conical incision to insertthe tip of at least one phacoemulsification handheld surgical implement,or handpiece. The handpiece includes a needle that is ultrasonicallydriven once placed within an incision to emulsify the eye lens, or breakthe cataract into small pieces. The broken cataract pieces maysubsequently be removed using the same handpiece or another handpiece ina controlled manner. The surgeon may then insert lens implants in theeye through the incision. The incision is allowed to heal, and theresults for the patient are typically significantly improved eyesight.

As may be appreciated, the flow of fluid to and from a patient through afluid infusion or extraction system and power control of thephacoemulsification handpiece is critical to the procedure performed.Different medically recognized techniques have been utilized for thelens removal portion of the surgery. Among these, one popular techniqueis a simultaneous combination of phacoemulsification, irrigation andaspiration using a single handpiece. This method includes making theincision, inserting the handheld surgical implement to emulsify thecataract or eye lens. Simultaneously with this emulsification, thehandpiece provides a fluid for irrigation of the emulsified lens and avacuum for aspiration of the emulsified lens and inserted fluids.

Pulse delivery has developed from a simple on/off arrangement throughwhat is known as a burst delivery or pulse delivery, using fixed offperiods or fixed duty cycles, to a specific pulse delivery such as theWhitestar pulse delivery method of Advanced Medical Optics Corporationof Santa Ana, Calif. Such designs provide the surgeon with differentfunctionality useful in different phacoemulsification procedures, suchas breaking the lens or removing the lens.

Previous systems have employed either an optimum phase angle to affectconstant energy transfer into the tissue or apply a modulated voltageamplitude shaping pulse to control the phacoemulsification handpiece.These procedures can produce a significant amount of heat in theaffected area. Care must be taken to avoid overheating of eye tissueduring phacoemulsification while still performing the desired cutting orremoval procedures. The risk of damaging the affected area viaapplication of heat can be a considerable negative side effect.

Conditions may arise during ocular surgeries that reduce the cuttingeffectiveness of current pulse shaping designs. In particular, oneundesirable effect exhibited by these systems is that small particles atthe phaco tip can be knocked off from the tip at an undesirable time.The phaco tip must be sufficiently occluded by, or in contact with, theparticle in order to effectively remove such particles. In order tocircumvent or manage this effect, surgeons typically reduce the voltageamplitude shaping pulse to keep small particles from being knocked offat the tip. This method of reducing the voltage amplitude can materiallylimit cutting effectiveness. In general, blockage of the phaco tipdramatically reduces cutting effectiveness, as does any overallreduction in voltage amplitude applied.

Typical available systems may employ what is known as an occluded mode,wherein an occlusion or blockage of the phaco tip, such as by a piece oflens, is addressed in some manner. The typical way of addressingocclusion has been to cease operation until the tip is no longeroccluded, i.e. simply releasing the pressure applied to the tip. Thisenables the operator/surgeon to manually move the tip and allow theocclusion to disengage from the instrument. such an implementationsimply monitors the pressure of vacuum on the tip, and when it exceeds acertain amount, the vacuum is released or no longer applied.

Increased efficiency in this environment is desirable, such that anydevices or procedures that can lessen heat applied to the affected areaor simplify the work of the operator surgeon is beneficial. Patientrecovery time can be enhanced when desirable performance is provided,such as reduced heat to the affected region.

Based on the foregoing, it would be advantageous to provide a systemthat employs a wave pulse shaping mechanism that enables successfulsurgeries without delivering excessive heat to the surgical site, andallows operators to operate the phacoemulsification system effectivelyunder both occluded and non-occluded conditions. It would also bebeneficial to overcome the aforementioned drawbacks present inpreviously known ultrasonic tissue removal systems.

SUMMARY OF THE INVENTION

According to one aspect of the present design, there is provided amethod of delivering ultrasonic energy during a surgical procedure, suchas a phacoemulsification procedure. The method comprises applying atleast one pulse, and typically multiple pulses, each having a pulseshape. The pulse shape comprises a predetermined pulse shape portion andeither an increased energy portion comprising an increase in energyproportional to an increase in sensed aspiration vacuum pressure or adecreased energy portion comprising a decrease in energy proportional toa decrease in sensed aspiration vacuum pressure.

According to a second aspect of the present design, there is provided anapparatus comprising a device configured to encounter vacuum pressure atthe surgical area, a vacuum sensor configured to monitor vacuum pressureencountered by the device, and a computer configured to compute anultrasonic pulse profile for delivery to a needle configured to vibratebased on the ultrasonic pulse profile received, the ultrasonic pulseprofile based on monitored vacuum pressure received from the vacuumsensor. The ultrasonic pulse profile comprises a baseline ultrasonicpulse region and an altered ultrasonic pulse region, the alteredultrasonic pulse region comprising a pulse portion altered based onmonitored vacuum pressure.

These and other advantages of the present invention will become apparentto those skilled in the art from the following detailed description ofthe invention and the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which:

FIG. 1 is a functional block diagram of a phacoemulsification system inaccordance with the present invention;

FIG. 2 is a flowchart illustrating the operation of aphacoemulsification system with variable ultrasonic power levels;

FIG. 3 illustrates a standard phacoemulsification ultrasonic wave shape,actual vacuum on aspiration line, and a calculated pulse shape amplitudewaveform;

FIG. 4 illustrates a calculated pulse shape amplitude waveformsuperimposed on a standard phacoemulsification ultrasonic wave shape toproduce a pulse shape amplitude wave shape;

FIGS. 5A-F show alternate examples of wave shapes according to thepresent design; and

FIG. 6 shows an exemplary wave shape according to another embodiment ofthe present design.

DETAILED DESCRIPTION OF THE INVENTION

The following description and the drawings illustrate specificembodiments to enable those skilled in the art to practice the systemand method described. Other embodiments may incorporate structural,logical, process and other changes. Examples merely typify possiblevariations. Individual components and functions are generally optionalunless explicitly required, and the sequence of operations may vary.Portions and features of some embodiments may be included in orsubstituted for those of others.

Currently available phacoemulsification systems include a variable speedperistaltic pump, a vacuum sensor, an adjustable source of ultrasonicpower, and a programmable microprocessor with operator-selected presetsfor controlling aspiration rate, vacuum and ultrasonic power levels. Aphacoemulsification handpiece is interconnected with a control consoleby an electric cable for powering and controlling the piezoelectrictransducer. Tubing provides irrigation fluid to the eye and enableswithdrawal of aspiration fluid from an eye through the handpiece. Thehollow needle of the handpiece may typically be driven or excited alongits longitudinal axis by the piezoelectric effect in crystals created byan AC voltage applied thereto. The motion of the driven crystal isamplified by a mechanically resonant system within the handpiece suchthat the motion of the needle connected thereto is directly dependentupon the frequency at which the crystal is driven, with a maximum motionoccurring at a resonant frequency. The resonant frequency is dependentin part upon the mass of the needle interconnected therewith, which istypically vibrated by the crystal.

One similar system and design is illustrated in U.S. patent applicationSer. No. 10/387,335, entitled “Modulated Pulsed Ultrasonic PowerDelivery System and Method,” inventors Kenneth E, Kadziauskas et al.,filed Mar. 12, 2003, the entirety of which is incorporated herein byreference.

Power control of the phacoemulsification handpiece is highly critical tosuccessful phacoemulsification surgery. Certain previous systems addressthe requirements of power control for a phacoemulsification handpiecebased on the phase angle between the voltage applied to a handpiecepiezoelectric transducer and the current drawn by the piezoelectrictransducer and/or the amplitude of power pulses provided to thehandpiece. The typical arrangement is tuned for the particularhandpiece, and power is applied in a continuous fashion or series ofsolid bursts subject to the control of the surgeon/operator. In certaincircumstances, the surgeon/operator may wish to apply these power burstsfor a duration of time, cease application of power, then reapply at thisor another power setting. The frequency and duration of the burst istypically controllable, as is the length of the stream of bursts appliedto the affected area. The time period where power is not applied enablescavitation in the affected area, and broken lens sections may be removedusing aspiration provided by the handpiece or an aspiration apparatus.The on/off application of power facilitates breaking the cataract intopieces and relatively efficient removal thereof.

The present design provides a system and method for preciselycontrolling the movement of the phacoemulsification needle tip using apulse shape controlled, or partially based on, sensed vacuum pressure.Controlling particle movement at the needle tip may enable betterdestruction (i.e. emulsification) of large and small particles. Thepresent vacuum based design determines whether additional energy isrequired to bump or move a large particle away from the needle tip. Thesystem may determine less energy is needed to enable a smaller particleto be drawn to the needle tip. The present design can include a controlloop to sense and continuously monitor actual vacuum at the needle tip,and the design may vary the amount of ultrasonic power delivered to thesurgical area in response to the observed actual needle tip vacuum.Moreover, the present design may actively vary the amount of ultrasonicpower delivered based on the size of the particle, directly proportionalto measured vacuum.

FIG. 1 illustrates a phacoemulsification system in block diagram form.The system has a control unit 105, indicated by the dashed lines in FIG.1 that includes a source of pulsed ultrasonic power 107, amicroprocessor computer 109 that provides control outputs to ultrasonicpower level controller 111, and a vacuum source 115. A vacuum sensor 113may continuously monitor and report the actual value of vacuum observedon line 110 and may provide these values for input to computer 109representing the vacuum level, or actual vacuum level, received on theinput side of vacuum source 115. Vacuum source 115 represents a vacuumsource typically included within control unit or phacoemulsificationdevice 105, generating a vacuum and attached to the line 110 andinterfacing with computer 109 to provide actual vacuum pressure readingsdynamically and receive signals to, for example, increase or decreasevacuum applied. Vacuum source may be provided separately from controlunit 105.

The block representation of the handpiece 104 includes a needle andelectrical means, typically a piezoelectric crystal, for ultrasonicallyvibrating the needle. The control unit 105 supplies power on line 102 toa phacoemulsification handpiece/needle 104. An irrigation fluid sourceis fluidly coupled to handpiece/needle 104 (not shown in FIG. 1). Theirrigation fluid at 116 and ultrasonic power at 117 are applied byhandpiece/needle 104 to a patient's eye, or affected area or region,indicated diagrammatically by block 106. Alternatively, the irrigationsource may be routed to the eye 106 through a separate pathwayindependent of the handpiece. The eye 106 is aspirated by the usingvacuum source 115 through line/handpiece needle 108 and line 110.Control unit 105 manages the amount of aspiration provided. A switch 112disposed on the handpiece 104 may be utilized to enable asurgeon/operator to select an amplitude of electrical pulses to thehandpiece via the computer 109, power level controller 111 andultrasonic power source 107 as discussed herein. Any suitable inputdevice such as for example, a foot pedal (not shown) may be utilized inlieu of the switch 112.

The control unit 105 may include a manual user interface 120 to allowthe surgeon/operator to preset various system parameters. User definedsystem parameters may include, but are not limited to, selecting pulseshape amplitude mode, setting maximum vacuum, minimum pulse shapeamplitude, and maximum pulse shape amplitude. In addition, the computer109 may provide operator-lettable limits for aspiration rates, vacuumlevels and ultrasonic power levels. The surgeon/operator may select thepulse shape amplitude (PSA) mode during any phase of an operationalprocedure via the manual user interface 120 console. Selection of PSAmode may direct the microprocessor computer 109 to continuously monitorthe resultant vacuum at line/handpiece needle 108 by measuring thepressure on line 110 via vacuum sensor 113. The computer 109 may respondto a surgeon selected preset maximum vacuum level and preset minimum andmaximum PSA values using signals from the vacuum sensor 113. If thereceived vacuum from vacuum sensor 113 exceeds a maximum vacuum level asset by the surgeon, an occluded condition exists, and the system canhalt vacuum pressure in an effort to enable occlusion removal.

Operation of the control unit 105 in response to an occluded-unoccludedcondition of handpiece 104 is shown in the flow diagram of FIG. 2. Anoccluded handpiece/needle 104 condition may arise when a large particlebecomes held by vacuum at the handpiece/needle 104 tip. This situationis found to reduce the phacoemulsification cutting efficiency.Furthermore, large particles tend to be more readily emulsified when theparticle is moved away from the handpiece/needle 104 tip. Conversely, anunoccluded handpiece/needle 104 may arise when a small particle is notheld firmly in position and may fall off the handpiece/needle 104. Inthis situation, a reduction in ultrasonic power delivered may allow thesmaller particle to be moved closer to the needle tip and may improvesmall particle destruction.

The present design may continuously vary the ultrasonic power deliveredto the surgical area in response to particle size as determined byactual vacuum present on the aspiration line 108. Although the presentdesign is described in terms of varying pulse shaping amplitude as afunction of vacuum, alternate embodiments of the present design mayinclude varying other system parameters such as phaco power and dutycycle as a function of vacuum, vacuum level, or vacuum pressure. Notethat as used herein, the term “vacuum” is intended to mean any type ofnegative pressure, including a vacuum condition, vacuum level, or vacuumpressure.

As illustrated in FIG. 2, the surgeon/operator may enable PSA mode atpoint 201. The present design may continuously monitor actual vacuumlevel at point 202, where actual vacuum level represents the vacuumlevel present on line/handpiece needle 108 and line vacuum line 110.Microprocessor computer 109 may calculate a desired PSA level at point203, where desired PSA level is typically a function of actual vacuumlevel, but may be a fixed value or function. The resulting PSA levelobtained from this calculation may indicate to computer 109 a need tochange the PSA level. Computer 109 may change the amount of ultrasonicenergy delivered by supplying signals to power level controller 111 togenerate an PSA wave shape at point 204 to increase, decrease, ormaintain the amount of energy delivered. Power level controller 111 maysuperimpose the PSA wave shape at point 206 with the standard wave shapeat point 205 resulting in an increase or decrease in ultrasonic powerdelivered based on actual vacuum level.

In this manner, the present design may dynamically change the totalamount of energy delivered to the surgical area in real-time based onconditions encountered, specifically vacuum pressure received or sensed.The present design may provide a continuous control loop for increasingor decreasing the amount of ultrasonic energy delivered by performing anPSA wave shape function at point 207 based on the combination of thestandard wave shape at point 205 modified by the PSA waveform at point204 in response to measured vacuum. If the surgeon/operator elects todisable the PSA mode at point 201, the phacoemulsification systemgenerates the standard phaco wave shape (e.g. burst, pulsed, etc.) atpoint 208 and performs the standard phaco wave shape at point 209.

The present design may calculate the pulse shape amplitude based on thefollowing equation:PSA=MinAmp+[(ActualVac)*(MaxAmp−MinAmp)]/(MaxVac)  (1)where: MaxAmp=maximum pulse shape amplitude, MinAmp=minimum pulse shapeamplitude, ActualVac=actual vacuum, MaxVac=maximum vacuum, and PSA=pulseshape amplitude.

Equation (1) provides valid pulse shape amplitude values for MaxVacvalues greater than zero, Table 1 provides resultant PSA valuescalculated based on an example of an implementation of Equation (1)using the following values:MaxVac=200 mm/hg;MinAmp=10%; and

MaxAmp=40%, where the percentage value represents percent aboveunmodified signal amplitude, 10% represents 10 percent above existing ornominal amplitude, or 110% of nominal,

TABLE 1 Example of Calculated PSA Versus Actual Vacuum ActualVac PSA 010% 10 11.5%   20 13% 40 16% 60 19% 80 22% 100 25% 150 32.5%   200 40%

PSA is calculated as a percentage of the nominal wave amplitudegenerated by the phaco system, FIG. 3 illustrates the relationshipsbetween a standard phacoemulsification ultrasonic wave shape, actualvacuum measured on the aspiration line, and a calculated pulse shapeamplitude waveform. Graph A in FIG. 3 represents an exemplary burst modephaco wave shape with a duty cycle of 33%. The ultrasonic power on timeis shown at point 301 with fixed amplitude. The ultrasonic power offtime is shown at point 302. Although a phaco burst mode wave shape isshown, the present design may be applied to any standard or evennon-standard phaco wave shape including a shape generated using pulsemode. Burst mode and pulse mode wave shapes known in the art. Graph B inFIG. 3 represents an example of actual vacuum measured on the aspirationline. In this example, the linear increase in vacuum pressure shown atpoint 303 may represent a larger particle beginning to occlude the phacotip opening. Although the example is shown as having a linear increasein vacuum for simplicity, the present design may accommodate any dynamicchanges in actual real-time vacuum. This occlusion may cause vacuum tobuild to a higher level as the phaco tip becomes more completely blockedoff. The vacuum level at point 304 represents reaching the MaxVac aspreset by the surgeon/operator in this example. This may represent acompletely blocked off or occluded phaco needle tip.

The vacuum level at point 305 may represent a decrease in vacuum as thelarge particle is bumped or moved away from the phaco needle tip.Movement may result in a decrease in observed vacuum present of theaspiration line. The vacuum level at point 306 is representative of alarge particle being precisely held away from the tip to ensure the mostefficient destruction or emulsification of the large particle. Thepresent design may generate the pulse shape amplitude waveformrepresented in Graph C in FIG. 3 based on the observed vacuum (Graph B)and the standard phaco wave shape either selected or provided (Graph A).

Based on the PSA equation, the present design may generate the pulseshape amplitude waveform with an ultrasonic on time at point 310 and offtime at point 311. This generated PSA waveform amplitude is 10 percentgreater than the standard wave shape shown in Graph A in accordance witha measured vacuum of 0 mm/hg. As vacuum pressure increases from 0 mm/hgto 200 mm/hg, the present design may generate the PSA waveforms shown atpoints 312, 313, 314 and 315. The PSA waveform increases proportionallyto actual vacuum until the MaxVac value is reached.

In this example, the present design may generate a PSA waveform withamplitude 40 percent greater than the standard phaco wave shape shown inGraph A. The actual vacuum at point 304 may represent an occluded phaconeedle tip. As the phaco power is increased via the PSA waveformaugmentation to the standard or nominal waveform, the large particle maybegin to move away from the needle and thus cause a drop in vacuum atpoint 305. As the large particle moves away from the Phaco needle tip,the needle tip may hold the large particle at a distance from the needletip, enhancing emulsification of the particle. Large particle movementmay be controlled or held in the present design by reducing the PSAwaveform amplitude at point 316 in accordance with actual vacuum atpoint 306.

The amplitude of the wave generated may vary, but also the duration ofthe pulse and the additional amplitude spike may vary depending oncircumstances. In general, a fairly short amplitude spike is added tothe nominal waveform, where amplitude of the spike is dependent upon thecalculation of Equation (1) or some similar vacuum based function.

FIG. 4 illustrates a calculated pulse shape amplitude waveform 401superimposed on a standard phacoemulsification ultrasonic wave shape 402in Graph A. The present design may combine or sum these two ultrasonicpower signals to produce a modified ultrasonic wave shape forphacoemulsification as shown in Graph B of FIG. 4. This combination mayform the pulse shape amplitude wave shape, Graph B represents a PSA waveshape in accordance with the vacuum profile shown in Graph B of FIG. 3.The ultrasonic profile represented at point 403 shows a 10% increase inamplitude generated by the present design for an actual vacuum of 0mm/hg. The ultrasonic profile represented at point 404 shows a 40%increase in amplitude generated by the present design for an actualvacuum of 200 mm/hg. The ultrasonic profile represented at point 405shows a 25% increase in amplitude generated by the present design for anactual vacuum of 100 mm/hg.

The ultrasonic power wave shape shown in Graph B of FIG. 4 represents anunoccluded condition at point 403, followed by an occluded condition atpoint 404 as a large particle is drawn closer and held at the phaconeedle tip opening. Movement of the large particle away from the phaconeedle tip occurs at point 405 due to the increased phaco powerdelivered at point 404. This increased power moves or bumps the largeparticle away from the phaco needle tip. In this automatedconfiguration, the present design may enable the surgeon/operator to useless force to dissipate an occlusion by increasing the ultrasonic poweras vacuum increases, thereby allowing the particle to be held firmly inposition during emulsification. The present design may indicate to thesurgeon the size of the particle by observing actual vacuum. Inaddition, the control loop mechanism within the present design mayenable the surgeon to self-feed said particles at the phaco needle tip.The ability to self-feed large and small particles may eliminate theneed for a second surgical instrument to push particles towards thephaco tip, as required by many currently deployed systems.

The present design has been described using an exemplary square wavephacoemulsification burst mode wave shape. As noted, although thedescription relates to how the present design modifies the amplitude ofa standard pulse wave shape, the present design may alternately oradditionally modify the width of the PSA waveform. In this arrangement,additional ultrasonic power may be delivered to the surgical area asrequired.

The illustrations presented in FIGS. 5A-5F illustrate pulses providedwith enhanced amplitude that vary in duration, from a small percentageof the overall pulse width to a large percentage of pulse width. FIG. 5Aillustrates one embodiment of a PSA wave shape. FIG. 5B illustrates aPSA wave shape with an increase in pulse shape amplitude over that shownin FIG. 5A. FIG. 5C illustrates an exemplary PSA wave shape wherein thewidth of the PSA waveform has been increased over that shown in FIG. 5A.Similarly, FIG. 5D illustrates an exemplary PSA wave shape wherein thewidth of the PSA waveform has been increased over that shown in FIG. 5B.FIG. 5E illustrates an exemplary PSA wave shape wherein the width of thePSA waveform has been increase over that shown in FIG. 5C, and FIG. 5Fillustrates an exemplary PSA wave shape wherein the width of the PSAwaveform has been increase over that shown in FIG. 5D.

The present design may modify amplitude and width of the PSA waveform inorder to provide the desired ultrasonic power for efficientphacoemulsification of large and small particles.

The present design is not limited to generating square waves in responseto the standard generated phaco wave shape. Other similar waveforms maybe employed and depend on the environment encountered, including but notlimited to phaco conditions, tip size, operating frequency, fluidconditions, and occlusion conditions. FIG. 6 illustrates an alternateaspect of the invention wherein rounded wave 600, or graduated powerdelivery curves are applied to the surgical area. In general, therounded waveform follows the teachings presented herein, wherein pulseapplied is based on vacuum pressure received and comprises a PSAenhanced amplitude region and a standard wave region. Other waveformsmay be employed but are generally based in some form on vacuum pressureencountered.

A further aspect of the present design may include varying the time andpower levels based on actual vacuum to attain transient cavatation asquickly as possible in the surgical environment without generatingsignificant heat in the region. As may be appreciated by those skilledin the art, sufficient power is delivered based on the circumstancespresented to induce transient cavatation, typically by delivering aninitial higher power surge or burst of energy, followed by a drop off inenergy from the initial surge in accordance with the present design.

Thus the present design delivers ultrasonic energy during a surgicalprocedure, such as a phacoemulsification procedure, and comprisesapplying at least one pulse and typically multiple pulses each having apulse shape. The pulse shape comprises a predetermined pulse shapeportion and either an increased energy portion comprising an increase inenergy proportional to an increase in sensed aspiration vacuum pressureor a decreased energy portion comprising a decrease in energyproportional to a decrease in sensed aspiration vacuum pressure.Alternately, the design monitors actual vacuum pressure level at thesurgical region, dynamically calculates a pulse shape amplitude (PSA)level based on monitored actual vacuum pressure level, generates a PSAwaveform based on the dynamically calculating, and sums a predeterminedwave shape with the PSA waveform to produce a PSA wave shape. The designthen delivers the PSA wave shape to a handpiece.

The design may be embodied in an apparatus comprising a deviceconfigured to encounter vacuum pressure at the surgical area, a vacuumsensor configured to monitor vacuum pressure encountered by the device,and a computer configured to compute an ultrasonic pulse profile fordelivery to a needle configured to vibrate based on the ultrasonic pulseprofile received, the ultrasonic pulse profile based on monitored vacuumpressure received from the vacuum sensor. The ultrasonic pulse profilecomprises a baseline ultrasonic pulse region and an altered ultrasonicpulse region, the altered ultrasonic pulse region comprising a pulseportion altered based on monitored vacuum pressure.

As may be appreciated by those skilled in the art, the present designmay be realized in software executing in microprocessor computer 109, ormay be implemented with dedicated microcontrollers or analog circuitry.

The foregoing is not determinative or exclusive or inclusive of allcomponents, interfaces, communications, and operational modes employablewithin the present design. The design presented herein and the specificaspects illustrated are meant not to be limiting, but may includealternate components while still incorporating the teachings andbenefits of the invention, namely a method of generating a pulse shapeamplitude in an arrangement that modifies phaco ultrasonic powerdelivered proportional to actual vacuum present. While the invention hasthus been described in connection with specific embodiments thereof, itwill be understood that the invention is capable of furthermodifications. This application is intended to cover any variations,uses or adaptations of the invention following, in general, theprinciples of the invention, and including such departures from thepresent disclosure as come within known and customary practice withinthe art to which the invention pertains.

What is claimed is:
 1. An apparatus for controlling ultrasonic powerdelivery to a surgical area, comprising: a device configured toencounter vacuum pressure at the surgical area; a vacuum sensorconfigured to monitor vacuum pressure encountered by said device; and acomputer configured to compute an ultrasonic pulse profile for deliveryto a needle configured to vibrate based on the ultrasonic pulse profilereceived, the ultrasonic pulse profile based on monitored vacuumpressure received from the vacuum sensor, wherein the computer isfurther configured to compute and apply at least one pulse to theneedle, each pulse having an ultrasonic pulse shape formed based onactual sensed vacuum pressure; wherein the formed ultrasonic pulse shapecomprises a predetermined ultrasonic pulse shape portion superimposed onan altered ultrasonic pulse shape portion; wherein the alteredultrasonic pulse shape portion is either an increased energy portioncomprising an increase in energy proportional to an increase in sensedvacuum pressure or a decreased energy portion comprising a decrease inenergy proportional to a decrease in sensed vacuum pressure, and whereinthe increased energy portion and decreased energy portion are determinedbased upon a ratio of actual sensed vacuum pressure to maximum sensedvacuum pressure, taking into account the maximum pulse amplitude andminimum pulse amplitude.
 2. The apparatus of claim 1, wherein the devicecomprises the needle.
 3. The apparatus of claim 2, wherein the computerdelivers the ultrasonic pulse profile to the needle so that movement ofthe needle induces transient cavitation within fluid within the surgicalarea.
 4. The apparatus of claim 2, wherein the surgical area is an eyeand the apparatus is for controlling ultrasonic power delivery during aphacoemulsification procedure.
 5. The apparatus of claim 1, wherein theneedle is within a second device.
 6. The apparatus of claim 5, whereinthe computer delivers the ultrasonic pulse profile to the needle so thatmovement of the needle induces transient cavitation within fluid withinthe surgical area.
 7. The apparatus of claim 5, wherein the surgicalarea is an eye and the apparatus is for controlling ultrasonic powerdelivery during a phacoemulsification procedure.
 8. The apparatus ofclaim 1, wherein the computer delivers the ultrasonic pulse profile tothe needle so that movement of the needle induces transient cavitationwithin fluid within the surgical area.
 9. The apparatus of claim 1,wherein the surgical area is an eye and the apparatus is for controllingultrasonic power delivery during a phacoemulsification procedure. 10.The apparatus of claim 1, wherein the increased energy portion and thedecreased energy portion are computed based on actual sensed vacuumpressure multiplied by maximum pulse amplitude minus minimum pulseamplitude and divided by maximum sensed vacuum pressure, added tominimum pulse amplitude.
 11. The apparatus of claim 1, wherein thecomputer is configured so that the applying comprises applying multiplepulses each comprising an individual pulse shape formed based on actualsensed vacuum pressure.
 12. The apparatus of claim 1, wherein the vacuumpressure is an aspiration vacuum pressure.